水库网箱养殖香鱼技术

香鱼(Plecog lossus altivelis)属鲑形目、胡瓜亚目、香鱼科、香鱼属，为一年生小型经济鱼类，一般个体重100～150克，最大达250～300克。香鱼分洄游型和陆封型两个品系，前者分布于有入海口的河川中，后者分布于水库湖泊里。陆封型香鱼个体小，繁殖力差。成体香鱼呈纺缍型，背部灰黑色，体侧银白色，各鳍末端淡黄色，胸鳍上方有一黄色斑块。香鱼肉质细嫩，味道鲜美，其脊背上有一条满是香脂的腔道，具有浓厚的诱人香味，深受消费者青睐，素有“淡水鱼之王”美称，是近年新兴的人工养殖珍稀新品种。福建省古田县水产技术推广站于2000年3月…     

香鱼(Plecoglossus altivelis)人工繁殖试验报告

<正> 香鱼是一种小型经济鱼类,它具有黄瓜味,被称为香鱼,我省有的地区称为“海胎鱼”。这种鱼分布在我国沿海几个省份(辽宁、河北、山东、福建、浙江、台湾)的河流和水库中。香鱼分“陆封型”和“洄游型”二个类别,据文献记载,我国台湾省和辽宁省的大伙房水库中有“陆封型”的香鱼,我省目前还未发现“陆封型”香鱼,只有洄游型的种类。在50年代至60年中期,我省香鱼产量约为3～4万斤左右,最大个体达半斤以上。但从60年代中期至今,由于兴修水利、工业污水等因素影响,香鱼产量逐年下降,鱼的个体也逐渐变小,目     

水库网箱养殖香鱼技术

香鱼（ｐｌｅｃｏｇ ｌｏｓｓｓｕ　ａｌｔｉｖｅｌｉｓ）属鲑形目、胡瓜亚目、香鱼科、香鱼属。为一年生小型经济鱼类，一般个体尾重１００－１５０，最大达２５０－３００ｇ。香鱼分洄游型和陆封型两个品系，前者多布于有人海口的河川中，后者分布于水库湖泊里。陆封型香鱼个体小，繁殖力差。成体香鱼呈纺锤型，背部灰黑色，体侧银白色，各鳍末端淡黄色，胸鳍上方有一黄色斑块。香鱼肉质细嫩，味道鲜美。其脊背上有一条满是香脂的腔道，具有浓厚的诱人香味，深受国内外消费者青睐。福建省古田县水产技术推广站于２０００年３月至１１月，…     

浅析碧流河水库陆封型香鱼消亡原因及恢复措施

1982年碧流河水库建成后,其库内洄游型香鱼形成陆封型种群.现有的捕捞数据表明,1999年以来,碧流河水库香鱼资源量锐减,该种群极有可能在碧流河水库内消失.对碧流河水库陆封型香鱼消亡的原因进行了分析,并就恢复措施进行了探讨.认为陆封型香鱼柄息环境恶化、自身不利变异、敌害鱼类和竞争鱼类抑制作用以及人为活动的破坏导致了碧流河水库陆封型香鱼的消亡;针对上述问题,积极有效的措施是通过实施人工增殖放流、控制敌害鱼类和竞争鱼类数量加强对香鱼资源的恢复和保护.     

图们江马苏大麻哈鱼陆封型的生物学资料

本文对628尾图们江马苏大麻哈鱼陆封型的一些生物学资料进行研究。结果表明鱼群由1—6龄组成，主要是2—4龄。我们首次发现雌鱼绝大多数个体(99．4％)终生不性成熟，性腺滞于Ⅱ期，故他们自繁能力极低。陆封型与洄游型关系密切。他们的产卵期与产卵场环境相同，前者雌雄比为1：1．7，后者为8：1，前者雄鱼参与后者繁殖，其性比恰呈互补，主食落入水中的陆生昆虫。建议保护陆封型资源。     

香鱼及其养殖

1香鱼概况 香鱼属鲑形目、胡瓜鱼亚目、香鱼科,为一年生小型鱼类,在全球分布区域很窄．仅限于从日本北海道到琉球群岛、朝鲜半岛、我国台湾岛及黄海、渤海、东海沿岸的通海河川中。约在10万年前,在日本琵琶湖中形成了纯淡水种群。进入现代社会,人们兴修水利阻隔了香鱼洄游通道,使香鱼在湖库中定居成为陆封型香鱼。     

利用养鳗池养殖香鱼的技术要点

香鱼是一种肉味鲜美,价格高昂的理想养殖品种。香鱼分陆封型和涸游型两类,陆封型个体较小,洞型游香自最大可达30厘米。洞游型香鱼在淡水中生长,在自然环境中每年的秋末初冬,随溪流到河口入海处产卵孵化,幼苗阶段生活在咸淡水域中,仔鱼变态长出鳞片后,再溯河到溪流淡水中生长,食物以底栖藻类为主。香鱼在日本、韩国和我国台湾都有很大的消费量,而且市场价格不菲,目前国内（浙江、福建）的价格也已达100－180元／公斤,而目前大多数养鳗场都面临着养鳗亏本的情景,香鱼则是很好替代更新的品种之一。利用养鳗场养殖香鱼的环境条件：…     

浙江省景宁陆封型香鱼卵巢发育的组织学

采用常规石蜡切片,H.E染色法研究了浙江省景宁县陆封香鱼(Plecoglossus altivelis)各期卵巢发育和组织学结构特征.结果表明:陆封香鱼卵巢发育可分为6个时期.7月份部分性腺为细线状,属于Ⅰ期卵巢;7月份和8月份香鱼性腺为Ⅰ期或者Ⅱ期,7月份和8月份的平均成熟系数分别为1.28％ 和1.45％;9月份,...     

陆封型马苏大麻哈鱼人工繁殖关键技术

正马苏大麻哈鱼在我国分布于图们江、绥芬河、台湾的大甲溪中。国内每年人工繁殖洄游型群体进行人工放流,对陆封型群体这一宝贵资源没有充分重视。2012年北京市鲟鱼鲑鳟鱼创新团队成立后,从吉林图们江引进陆封型马苏大麻哈鱼,开展了人工选育、繁殖和养殖技术研究。马苏大麻哈鱼Oncorhynchus masou(Brerart),属鲑形目、鲑科、大麻哈鱼属。是北太平洋水域大麻哈鱼类之一,仅分布亚洲一测水域,是大麻哈鱼类中分布地理纬度较低、栖息水温较高的种类。为溯河洄游性鱼     

北极红点鲑人工繁育技术

北极红点鲑(Salvelinus alpinus)在鱼类分类学上隶属鲑形目、鲑科、红点鲑属,主要分布在加拿大、美国、瑞典、奥地利、芬兰、俄罗斯、挪威、英国等国家和地区,是生活在地球最北的淡水鱼,也是最寒冷地区的鱼. 北极红点鲑分为洄游型和陆封型两种,海河洄游型红点鲑为银色,且带有红斑点,可长到12kg左右;陆封型湖泊红...     

Characterization of the digestive tract of wild ayu

ABSTRACT: The gut and gut contents of ayu Plecoglossus altivelis caught in the Ohta River in Hiroshima prefecture, Japan were examined. Relative intestine length (intestine length/body length) was almost constant. Except for relative intestine length, characteristics of the gut of wild ayu were not significantly different from those of cultured ayu. The height of intestinal folds increased and their width declined from stomach to anus. Cyanobacteria ( Homoeathrix sp. and Calothrix sp.) and diatoms ( Cymbella sp., Gomphonema sp., Melosira sp., Navicula sp., and Synedra sp.) were well digested during passage through the gut despite a lack of apparent destruction. In contrast, green algae ( Dictyosphearium sp., Coelastrum sp., and Pediastrum sp.) exhibited little degradation. The pH of stomach contents ranged from 2.8 to 7.4 (mean ± SD = 4.1 ± 1.0), whereas that of the posterior intestine was 7.0–8.5 (7.9 ± 0.4). Gut contents of wild ayu increased with bodyweight, and were more than threefold greater than those of cultured ayu, suggesting that wild ayu compensate for low nutrient content of algae through the continuous ingestion of large quantities of feed organisms.     

Growth of Flavobacterium psychrophilum in fish serum correlates with pathogenicity

Flavobacterium psychrophilum isolates, obtained from ayu, Plecoglossus altivelis, three species of salmonids and two species of cyprinids in Japan, were used in this study. Bacteria were inoculated to serum prepared from ayu or red spotted masu trout (RSMT), Oncorhynchus masou ishikawae, and incubated at 18 °C for 24 h. All isolates (n = 19) from ayu grew well with a 9- to 116-fold increase of CFU in ayu serum, while CFU decreased markedly in RSMT serum. In contrast, isolates (n = 17) from fish species other than ayu exhibited no growth in ayu serum, but some isolates from salmonids survived or grew (1.2-23.5 fold increase of CFU) in RSMT serum. The isolates that could not survive or grow in ayu and RSMT sera grew well in both heat-inactivated sera of ayu and RSMT. Experimental infection by intraperitoneal injection showed that ayu isolates examined were all pathogenic to ayu but not to RSMT, while none of the isolates from salmonids and cyprinids were pathogenic to ayu but some showed pathogenicity to RSMT. These results indicate that the in vitro growth ability of F. psychrophilum isolates in fish serum correlates well with their pathogenicity to fish, particularly in ayu.     

Residence pattern of the ayu <Emphasis Type="Italic">Plecoglossus altivelis</Emphasis><Emphasis Type="Italic">altivelis</Emphasis> larvae and juveniles occurring in the surf zone of a sandy beach,Niigata Prefecture,northern Sea of Japan

This study examined the residence pattern of ayu larvae and juveniles occurring in the surf zone of an extensive sandy beach, in the north part of the Sea of Japan. In this region, ayu larvae mainly hatched in October and November, generally appeared in the surf zone in hatching order, and were continuously present until the following January. During a short period after mid- to late January when the water temperature fell below 10°C, ayu larvae and juveniles concurrently migrated from the surf zone regardless of their size and age, resulting in a longer term residence for earlier-hatched ayu. This was in contrast to studies in other waters, which found that early-hatched ayu have a short-term residence and late-hatched a long-term residence. Furthermore, faster growth that enables ayu to reach the maximum residence size (around 40 mm BL) in the surf zone during the period when the water temperature was still over 10°C might lead to earlier migration and a shorter residence term. This process might be applicable only to the early-hatched group (defined as individuals hatched in late September and October) and depends on the size of each individual, thus leading to a gradual migration of larger individuals as they attain maximum residence size.     

Feeding territory and variations in behavioural modes of algae‐grazing fish Plecoglossus altivelis ryukyuensis (Ryukyu‐ayu) in subtropical island streams

Abstract – Social and foraging modes in fish often vary between individuals with different body sizes and between populations under different ecological conditions. We studied social and foraging behaviour of algae‐grazing fish Plecoglossus altivelis ryukyuensis (Ryukyu‐ayu) inhabiting Japanese subtropical island streams. Ryukyu‐ayu exhibited four behavioural modes: territorial, schooling, solitary and floating. Their body sizes differed among these modes. Territorial fish predominantly foraged on benthic algae, whereas schooling and solitary individuals frequently consumed drifting materials as well. Schooling fish were smaller than territorial fish, but, unlike some other algae‐grazing fish species, did not use schooling to gain access to food within territories. Territorial fish attacked smaller conspecifics but exhibited lateral display towards larger fish and schooling fish while occasionally attacking grazing gobies. Larger fish maintained larger feeding territories and occupied territories for longer periods than smaller fish did. This suggests that, in Ryukyu‐ayu, intra‐ and interspecific food competitions and relative body size can influence diverse behavioural modes and duration of territory occupation. We also found that Ryukyu‐ayu foraged more often and had larger feeding territories than ayu P. a. altivelis inhabiting temperate streams. We conclude that foraging strategies of Ryukyu‐ayu may have adapted to subtropical island streams, where algal productivity is much lower than that in temperate regions.     

Molecular typing by pulsed-field gel electrophoresis of Flavobacterium psychrophilum isolates derived from Japanese fish

Sixty-four isolates of Flavobacterium psychrophilum from ayu, Plecoglossus altivelis altivelis (Temminck & Schlegel), and other fish (n=16) in Japan and the type strain (NCIMB 1947(T)) were typed using pulsed-field gel electrophoresis (PFGE) with endonuclease BlnI and XhoI. These isolates were classified into 20 clusters and 42 genotypes by PFGE analysis. The most predominant cluster of isolates from ayu was cluster XII (n=20), followed by clusters XVII, XVI, XX, XI, IX, X, XIII and XV; the remaining 17 isolates from other fish were divided into clusters I, II, III, IV, V, VI, VII, VIII, XIV, XVIII and XIX. The PFGE genotype of isolates from ayu clearly differed from those of other fish. The isolates from ayu in Gunma Prefecture belonged to clusters XII, XVI, XVII and XX, and the strains of three of these clusters (XII, XVII and XX) were isolated from ayu in 15 of 19 prefectures. PFGE typing enabled more accurate classification of isolates into clusters than previously achieved by analysing the restriction fragment length polymorphism of PCR products. These results suggest that F. psychrophilum isolated from ayu and other fish are genetically different and strains with several PFGE types have spread within Japan.     

A novel genotyping technique for distinguishing between Flavobacterium psychrophilum isolates virulent and avirulent to ayu, Plecoglossus altivelis altivelis (Temminck & Schlegel)

We developed a simple genotyping method for Flavobacterium psychrophilum for analysing two single nucleotide polymorphisms (SNPs) in the gyrA gene and to distinguish between isolates that are virulent and avirulent to ayu, Plecoglossus altivelis altivelis (Temminck & Schlegel). The genotyping method is an on/off switch assay and is based on the polymerase chain reaction technique with phosphorothioated primers. We classified 232 isolates from four families of fish (i.e. Plecoglossidae, Osmeridae, Cyprinidae and Salmonidae) into four genotypes (G‐C, A‐T, A‐C and G‐T). The G‐C type isolates exhibited strong pathogenicity to ayu, whereas the A‐T and G‐T types did not show any pathogenicity to this species. The A‐C type exhibited no or weak pathogenicity to ayu. These results indicate that genotyping F. psychrophilum isolates with two SNPs from gyrA can clearly distinguish between isolates potentially harmful to ayu (G‐C type) and those that are potentially not harmful or less harmful (A‐C, A‐T and G‐T type). The on/off switch assay provides a quick, simple, and very powerful DNA genotyping technique for F. psychrophilum isolates.     

The existence of extra-retinal and extra-pineal photoreceptive organ regulating gonadal development of ayu, Plecoglossus altivelis

The photoreceptors regulating photoperiodic gonadal development of ayu, Plecoglossus altivelis, are not known. In this study, we examined whether the gonads of ophthalmectomized and pinealectomized (Ex+Px) ayu respond to short photoperiod. Gonadosomatic index (GSI) and plasma levels of sex steroids were significantly increased in Ex+Px ayu kept under short photoperiod in both males and females. On the other hand, there were no significant increase in GSI and sex steroids in Ex+Px ayu kept under long photoperiod. The histological observation of the gonads revealed that oocytes undergoing final maturation in females and proliferation of germ cells in males were observed only in Ex+Px ayu kept under short photoperiod. Altogether, our results strongly suggest unknown photoreceptive organ regulates photoperiodic gonadal development of ayu.     

Early life‐history adaptation influences conservation approaches for facultatively amphidromous fish

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Turbid water induces refuge behaviour of a commercially important ayu: A field experiment for interstream movement using multiple artificial streams

Riverine systems are inherently dendritic in nature, and turbid water may not necessarily flow equally throughout an entire catchment. Tributaries have the potential to serve as refugia from temporarily turbid water in the main stem. As ayu (Plecoglossus altivelis) are one of the important species for the inland fisheries industry and recreational fishing, their behaviour in a branched river network is a primary concern. We released ayu with radio‐transmitting tags into two experimental streams that joined at a downstream pool. Turbid water was released into one of the streams, and we identified whether avoidance movement of ayu between the two experimental streams was triggered by flowing turbid water. The suspended solid concentration elevated rapidly after adding the turbid water and was maintained at more than 400 mg/L for 3 hr. Avoidance movement of ayu was triggered when the suspended solid concentration exceeded approximately 200 mg/L. Then, most ayu moved from the turbid stream to the nonturbid one, leading to a difference in ayu density between the two streams. Therefore, we demonstrated that turbid water induced interstream movement of a commercially important ayu as refuge behaviour, suggesting that river connectivity is important for the persistence of the ayu.     

Experimental analysis on the relationship between the population density of ayu Plecoglossus altivelis altivelis and fishery catch by “Tomozuri” angling

To investigate the relationship between the population density of ayu and the survival rate, number of ayu caught by “Tomozuri” angling and total fishery catch, ayu were introduced into experimental ponds with currents at densities of 1.1–6.1/m² in 2011 and 2012. After stocking in May, fishing was conducted from early July to late August or early September. The proportion of dead ayu in each pond was less than 20 % through the experiment and was not correlated with the initial density of ayu in either year. The growth rates of ayu that were fished and that remained in ponds to the end of the experiment were negatively correlated with the initial density. However, the number and catch of ayu fished by Tomozuri peaked at an initial density of 2.6–4.7/m². Medium- and large-sized ayu heavier than 30 and 50 g, respectively, caught by fishing peaked at initial densities of 2.6/m² and 2.1–2.6/m². These results suggest that the traditional criterion on the stock density of ayu, 0.6–0.7/m², is too low from the viewpoint of Tomozuri angling, and recent stock densities used in many prefectures, 0.5–2.0/m², are not sufficient.